136 MORPHOLOGY ASD EVOLUTION
m other Gibbons, and it is relatively wider in the Orang than in the Chimpanzee and Gorilla. In the Gorilla the neural foramina are relatively smaller than in Man. In the African Simiidoe the first sacral vertebra corresponds to the fifth lumbar vertebra in Man. Cunningham (391 has shown that a forward curvature of the lumbar region of the vertebral column is not a human character, for it is present in all the Apes. It is, however, feeble in the Orang. In the Chimpanzee it includes one or two sacral vertebrae; it is developed at an early age, and it becomes as strong as in Man. No promontory of the sacrum separates it from the very slightly concave sacrum. In the Gibbon it includes the five lumbar vertebrae, and a slight promontory limits it below. The Gorilla also has a lumbar curve, but at present it is not possible to give accurate details of its characters. The size of the lumbar curve is inversely proportional to the degree of extensibility of the hip-joint.
The vertebral ligaments are very elastic, particularly the ligamenta subfiava in the Gibbon; and this is of assistance in springing.
Pelvis (fig. 35).— The iliac bones in the Apes differ considerably from those in Man, but those in the Gorilla differ least. In the Gibbon they are prismatic and elongated, and the coarse ischial tuberosities support the ischial callosities; the tuberosities are not so flat as in the Drill and Mandrill.
In the Chimpanzee (fig. 26} the ilia are wider and flat, but they are wider and slightly concave in the Gorilla. The long axis of the pelvic cavity is antero-posterior in the Apes, and transverse in Man. The ischial spine is